Push button switch

Abstract

A push button switch which may be used, for example, as a zooming switch in a video camera, having a uniform electrical resistance/applied pressure characteristic and which can be manufactured easily and at a low cost. The switch includes a conductive layer and a pressure-sensitive resistance element disposed between electrode patterns provided on a printed circuit board and an insulated push button. The conductive layer is coated with a pressure-sensitive conductive paste and the pressure-sensitive resistance element is fixed to the insulated push button at a opposed surface to the electrode patterns separated by a predetermined distance.

What is claimed is: 
     
       1. A push button switch having a resistance value varying in response to variations in a pressure applied thereto, said push button switch comprising: a printed circuit board having electrode patterns;   a pressure-sensitive resistance element to be pressed against said electrode patterns, said pressure-sensitive resistance element comprising a conductive layer coated with a layer of solidified pressure-sensitive conductive paste and molded together by press curing under heat;   an insulated push button comprising a pressing surface at a base portion thereof, two projection portions at an upper portion of said insulated push button, and a flange portion fixed to said printed circuit board, said conductive layer of said pressure-sensitive resistance element being fixed to said pressing surface and being spaced from said electrode patterns by a predetermined gap, and said two projection portions being separated by a thin portion for allowing vertical movement of said insulated push button;   a button cover having two protrusions adjacent in one-to-one correspondence to said two projection portions, either of said protrusions exclusively pressing against one of said projection portions when said button cover is pressed by a user;   a shaft between said two projection portions for movably supporting said button cover on said printed circuit board, said button cover being movable in a seesawing motion; and   a supporting member fixed to said printed circuit board such that said flange portion is fixedly sandwiched between said supporting member and said printed circuit board.